CHAPTER
25
Diuretics
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25-2
Clinical Indication
• Diuretics are used to treat anuria,
hypertension, and edema.
• There are six classes of diuretics:
– Osmotic agents
– Carbonic anhydrase inhibitors
– Thiazide and thiazide-like compounds
– Organic acids
– Potassium-sparing diuretics
– ADH antagonists
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Renal Function
• The kidneys are responsible for urine
production.
• The working units of the kidney are
known as nephrons.
• The nephron is composed of several
segments.
• Urine is produced through filtration,
reabsorption, and secretion.
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Renal Function
• The renal mechanism for water
conservation is dependent upon
tubular reabsorption of sodium ions.
• The nephrons secrete hydrogen ions,
potassium ions, and weak acids and
bases to regulate acid-base balance
of the body.
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Renal Dysfunction
• Renal disease and cardiovascular
dysfunction alter the functioning of the
kidney, leading to:
– Decreased urine flow
– Decreased urine volume (oliguria)
– No urine production (anuria)
– Uremia
– Edema
– Hypotension
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Osmotic Diuretics
• Filtered by glomerulus but not reabsorbed
by renal tubules, creating osmotic gradient.
• Stimulate urine flow, producing mild
diuresis with no electrolyte imbalance.
• Adverse effects include nausea, dizziness,
headache, and chills. Mannitol is
contraindicated in patients with edema
from cardiovascular insufficiency,
pulmonary edema, or intracranial bleeding.
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Carbonic Anhydrase Inhibitors
• Increase sodium and water excretion
by inhibiting carbonic anhydrase:
– No hydrogen ions to exchange for sodium
ions
– Decreased sodium reabsorption
– Sodium ions and increased water excreted in
urine
– Increased loss of potassium in urine
– Decreased bicarbonate in blood (acidosis)
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Carbonic Anhydrase Inhibitors
• Used in the treatment of CHF or druginduced edema
• Reduce pressure with glaucoma
• Useful in the treatment of epilepsy
• Adverse effects:
– Drowsiness
– Headache
– GI distress
– Acidosis
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https://upload.wikimedia.org/wikipedia/common
s/7/72/Renal_Diuretics.gif
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Osmotics/Carbonic Anhydrase Inhibitors
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Thiazide and Thiazide-like Diuretics
• Inhibit sodium transport in the distal
portion of the nephron, causing substantial
loss of sodium and water
• Produce intense diuresis
• Can eliminate edema of any cause
• Useful in treatment of mild to moderate
hypotension
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Thiazide and Thiazide-like Diuretics
• Mobilization of sodium causes potassium
excretion as well (hypokalemia).
• Side effects include:
– Hyponatremia
– Orthostatic hypotension
– Hyperglycemia
– Muscle spasms or cramps
– GI distress
– Headache
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Thiazide and Thiazide-like Diuretics
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http://www.drugs.com/drug-class/thiazidediuretics.html
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Organic Acid Diuretics (loop diuretics)
• Inhibit sodium and chloride ion transport in
the loop of Henle
• Tremendous loss of sodium, chloride, and
water
• Highly bound to plasma proteins
• Used for treatment of edema in patients
who have become thiazide resistant
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https://quizlet.com/1905791/organic-aciddiureticsloop-diuretics-flash-cards/
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Organic Acid Diuretics
• Side effects are similar to thiazide
diuretics:
– Nausea
– Hypotension
– Hypokalemia
– Hyperuricemia
– Hyperglycemia
• Additional side effects include:
– Ototoxicity
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Potassium-Sparing Diuretics
• Inhibit potassium secretion in DCT
• Produce mild diuresis without electrolyte
or acid-base disturbances
• Side effects:
– Nausea
– Diarrhea
– Hyperkalemia
– Gynecomastia
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Organic Acid/Potassium-Sparing Diuretics
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ADH Antagonists
• ADH regulates water balance in the
body.
• ADH antagonists block the ADH
receptors in the kidneys.
• Inhibition of ADH receptors causes
excretion of free water without
electrolyte loss.
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25-21
Miscellaneous Diuretics
• Xanthine derivatives are naturally
occurring drugs that produce mild
diuretic responses.
• They stimulate urine flow by
increasing blood flow to kidneys.
• Side effects include CNS stimulation,
hypotension, and headache.
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Special Considerations
• Most diuretics cause electrolyte and
acid-base imbalance:
– Potassium loss is most common.
– Patients should supplement potassium.
• Blood pressure may be altered.
• Blood glucose levels may be altered.
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Drug Interactions and Incompatibilities
• Diuretics are involved in a number of
drug interactions due to their MOA:
– Bind to plasma proteins
– Alter acid-base balance
– Stimulate renal excretion
• Diuretics when mixed in IVs with
other solutions can cause precipitate
formation.
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25-24
Preferred Treatment
ADH Antagonists
Euvolemic and
hypervolemic
hyponatremia
Carbonic
Anhydrase
Inhibitors
Glaucoma, edema
with alkalosis and
mountain
sickness
Loop Diuretics
Pulmonary and
peripheral edema,
hypertension and
acute renal failure
Thiazides
Hypertension,
mild heart failure,
and
nephrolithiasis
Osmotic Diuretics
Improve renal
failure, reduce
intracranial
pressure,
glaucoma
Potassiumsparing Diuretics
Hypokalemia due
to other diuretics
and post MI
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